This application relates in general to electronic cables utilizing twisted pair technology for the transmission of balanced or unbalanced signals.
A twisted pair arrangement consists of two insulated conductors twisted about each other to form a two conductor group. When more than one twisted pair group is bunched or cabled together, it is referred to as a multi-pair cable. A problem encountered when using a multi-paired cable is that data transmitted on one pair can often interfere with the transmission of data on another pair within the multi-pair cable. This is due to the fact that all insulated conductors or pairs carrying data in the form of current will radiate an electric and magnetic field. This is commonly referred to as electro-magnetic noise interference, or EMI. The further away one wire is from another wire generating this interference, the less susceptibility there is to its effects.
One prior art method of distancing elements, in this case twisted pairs, is discussed in U.S. Pat. No. 4,873,393, assigned to AT&T. In '393 individual pairs have different nonsequentional laylengths. Laylength is a term referring to the axial distance required for one conductor to complete one revolution about the axis of another conductor. It is known that when adjacent twisted pairs employ the same twist frequency they tend to nest into each other, making each pair more susceptible to the other's emissions. By varying the laylengths, this nesting effect is reduced. However, problems still arise with this solution. An example illustrating the problem is realized when a twisted pair, whether varied in twist frequency or not, can have as many as six adjacent pairs surrounding it. Therefore, one pair can have up to six noise sources directly surrounding it.